Thread bonded with segmented copolyester elastomers

ABSTRACT

MULTI-FILAMENT THREAD BONDED WITH A THERMOPLASTIC SEGMENTED COPOLYESTER ELEATOMER CONSISTING ESSENTIALLY OF A MULITIPHICITY OF RECURRING SHORT CHAIN ESTER UNITS AND LONG CHAIN ESTERS UNITS JOIN THROUGH ESTER LINKAGES, SAID SHORT CHAIN ESTER UNITS AMOUNTING TO ABOUT 15 TO 65 PERCENT BY WEIGHT OF SAID COPOLYESTER AND BEING DERIVED FROM DICARBOXYLIC ACID SUCH AS TEREPHTHALIC ACID, OR A MIXTURE OF TEREPHTHALIC AND ISOPHTHALIC ACIDS, AND AN ORGANIC DIOL SUCH AS BUTANEDIOL, AND SAID LONG CHAIN ESTER UNITS AMOUNTING TO ABOUT 35 TO 85 PERCENT BY WEIGHT OF SAID COPOLYESTER AND BEING DERIVED FROM DICARBOXYLIC ACID SUCH AS TEREPHTHALIC ACID, OR A MIXTURE OF TEREPHTHALIC AND ISOPHTHALIC ACIDS, AND A LONG CHAIN GLYCOL SUCH AS POLYTETRAMETHYLENE ETHER GLYCOL, SAID COPOLYESTERS HAVING A MELT INDEX OF LESS THAN ABOUT 150 AND A MELTING POINT OF AT LEAST ABOUT 125* C. THE BONDING AGENT MAY BE MODIFIED WITH ONE OR MORE THERMOPLASTIC RESINS OR MODIFIERS.

United States Patent 3,823,031 THREAD BONDED WITH SEGMENTED COPOLYESTER ELASTOMERS Akira Tsukamoto, 4308 Miller Road, Apt. 207, Wilmington, Del. 19802, and Robert K. Tubbs, 589 Morgan Drive, Lewistou, N.Y. 14092 No Drawing. Filed Aug. 9, 1971, Ser. No. 170,287 Int. Cl. B32b 27/02 US. Cl. 117-1383 F 8 Claims ABSTRACT OF THE DISCLOSURE Multi-filament thread bonded with a thermoplastic segmented copolyester elastomer consisting essentially of a multiplicity of recurring short chain ester units and long chain ester units joined through ester linkages, said short chain ester units amounting to about 15 to 65 percent by weight of said copolyester and being derived from dicarboxylic acid such as terephthalic acid, or a mixture of terephthalic and isophthalic acids, and an organic diol such as butanediol, and said long chain ester unlts amounting to about 35 to 85 percent by weight of said copolyester and being derived from dicarboxylic acid such as terephthalic acid, or a mixture of terephthalic and isophthalic acids, and a long chain glycol such as polytetramethylene ether glycol, said copolyester having a melt index of less than about 150 and a melting point of at least about 125 C. The bonding agent may be modified with one or more thermoplastic resins or modifiers.

BACKGROUND OF THE INVENTION (1) Field of the Invention This invention relates to the method of bonding multifilament thread using a thermoplastic, segmented copolyester elastomer and to the resulting bonded thread.

(2) Description of the Prior Art Breakage of thread is a serious problem in commercial sewing operations. In the operation of high speed commercial sewing machines a tremendous amount of heat builds up at the needle. This can cause the thread to break, resulting in much loss of time by the machine operator during rethreading of the machine and a reduction in the through-put of the machine. This problem has been alleviated in the case of most nylon multi-filament thread by coating the thread with a nylon resin which bonds the filaments of the thread together, thereby increasing the thread strength, resulting in reduced breakage. Some nylon threads are more difi'icult to bond than others and thus there is a need for a bonding agent which is useful with a wide variety of nylon threads.

In order to be successful as a bonding agent for thread, the bonding agent must (1) hold the filaments and plies of the thread together, (2) adhere to the thread so that it is not scraped off as it passes through the eye of the needle, (3) have a high enough melting temperature that the coating does not melt under the heat of the needle, (4) be soluble in suitable solvents for application to the thread, and (5) be sufficiently elastomeric or flexible that the coating does not significantly stifien the thread.

In the case of polyester threads no commercially available bonding agent meets all of the above requirements. The major deficiency of these bonding agents with polyester thread is the lack of good adhesion. Accordingly, there is a need for an improved bonding agent for polyester thread which meets all of the above requirements.

SUMMARY OF THE INVENTION produced by the process which comprises coating a multi- 3,823,031 Patented July 9, 1974 filament thread with a bonding agent comprising a thermoplastic segmented copolyester elastomer consisting essentially of a multiplicity of recurring short chain ester units and long chain ester units joined through ester linkages, said short chain ester units amounting to about 15 to 65 percent by weight of said copolyester and being of the formula and said long chain ester units amounting to about 35 to percent by weight of said copolyester and being of the formula o 0 JRgOGO wherein R is the divalent radical remaining after removal of the carboxyl groups from dicarboxylic acid having a molecular weight of less than about 350, D is the divalent radical remaining after removal of the hydroxyl groups from organic diol having a molecular weight of less than about 250, and G is the divalent radical remaining after removal of the terminal hydroxyl groups from long chain glycol having an average molecular weight of about 350 to 6000, said copolyester having a melt index of less than about 150 and a melting point of at least about C.

DETAILED DESCRIPTION OF THE INVENTION In accordance with this invention multi-filament threads are coated with a bonding agent comprising a thermoplastic segmented copolyester elastomer. The resulting coated threads have excellent properties. When multi-filament thread is coated in accordance with this invention, the filaments and/or plies of the thread are not readily separated by untwisting, the coating is not readily peeled from the thread by abrasion, the coating provides good heat dissipation as manifested by good slip characteristics through the needle, and the coated thread has good flexibility. In the case of polyester threads, the coated thread is superior to coated polyester threads heretofore commercially available. In the case of nylon thread, excellent results are obtained even in the case of diflicult to bond nylon thread.

The process of this invention is suitable for use with all multi-filament threads. The term multi-filament is intended to include threads having two or more filaments held together such as by twisting. The term thread is intended to include a continuous strand of any size which is suitable for sewing and which may be constructed of one or more plies. Thus this term in appropriate cases may include yarn, string, cord, rope, and the like. The thread filaments may be polyester, nylon, cotton, and the like. The process of this invention is generally applied to polyester and nylon threads since their greater strength makes them the threads of choice in commercial sewing operations.

The thermoplastic segmented copolyester elastomers used as bonding agents in accordance with this invention consist essentially of 15 to 65 percent recurring short chain ester units and 35 to 85 percent long chain ester units joined through ester linkages. The term consisting essentially of, as used herein, is meant to include in the copolyester only those unspecified polymer units which do not materially affect the basic and essential characteristics of the copolyester for use in accordance with this invention. In other words, this term excludes unspecified polymeric units in amounts which prevent the advantages of its use in accordance with this invention from being realized. The term short chain ester units, as applied to units in a polymer chain, refers to the reaction products of low molecular weight diols with dicarboxylic acids to form repeat units having molecular weights of less than about 550. These units are also referred to herein as hard segments. The term long chain ester units, as applied to units in a polymer chain, refers to the reaction products of long chain glycols with dicarboxylic acids. These units are also referred to herein as soft segments.

The copolyesters used in accordance with this invention are prepared by polymerizing with each other (a) one or more dicarboxylic acids, (b) one or more linear long chain glycols, and (c) one or more low molecular weight diols. The term dicarboxylic acid, as used herein, is intended to include the equivalents of dicarboxylic acids, that is, their esters or-ester-formiug derivatives such as acid chlorides and anhydrides, or other derivatives which behave substantially like dicarboxylic acids in a polymerization reaction with glycol.

The dicarboxylic acid monomers useful herein have a molecular weight of less than about 350. This molecular weight requirement pertains to the acid itself and not to its ester or ester-forming derivative. Thus, the ester of a dicarboxylic acid having a molecular weight greater than 350 is included in this invention provided the acid itself has a molecular weight below about 350.

The dicarboxylic acids used in the preparation of the segmented copolyester can be aromatic, aliphatic or cycloaliphatic. The dicarboxylic acids can contain any substituent groups or combination thereof which do not interfere with the polymerization reaction. Hydroxy acids such as p(}3-hydroxyethoxy) benzoic acid can also be used provided a dicarboxylic acid is also present.

Representative aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, bibenzoic acid, substituted dicarboxy compounds with benzene nuclei such as bis(p-carboxyphenyl) methane, p-oxy(pcarboxyphenyl) benzoic acid, ethylene-bis(p-oxybenzoic acid), ethylene-bis(p-benzoic acid), tetramethylene-bis- (p-oxybenzoic acid), 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, phenanthrene dicarboxylic acid, anthracene dicarboxylic acid, 4,4-sulfonyl dibenzoic acid, indene dicarboxylic acid, and the like, as 'well as ring substituted derivatives thereof such as C -C alkyl, halo, alkoxy or aryl derivatives. By the term aromatic dicarboxylic acid is meant a dicarboxylic acid in which each carboxyl group is attached to a carbon atom in an isolated or fused benzene ring or a ring which is itself fused to a benzene nng.

Representative aliphatic and cycloaliphatic dicarboxylic acids include sebacic acid, 1,3- (and 1,4-) cyclohexane dicarboxylic acids, adipic acid, glutaric acid, succinic acid, oxalic acid, itaconic acid, azelaic acid, diethylmalonic acid, maleic acid, fumaric acid, citraconic acid, allylmalonic acid, 4-cyclohexene-1,2-dicarboxylic acid, pimelic acid, suberic acid, 2,5-diethyl-adipic acid, 2-ethylsuberic acid, 2,2,3,3-tetramethylsuccinic acid, cyclopentanedicarboxylic acid, decahydro-1,5- (and 2,6-) naphthylene dicarboxylic acids, 4,4'-bicyclohexyl dicarboxylic acid, 4,4'-methylene-bis(cyclohexyl carboxylic acid), 3,4-furan dicarboxylic acid, and 1,1-cyclobutane dicarboxylic acid. The preferred aliphatic acids are the cyclohexanedicarboxylic acids and adipic acid.

The preferred dicarboxylic acids for preparation of the segmented copolyester are the aromatic acids of 8 to 16 carbon atoms, particularly phenylene dicarboxylic acids such as phthalic, terephthalic and isophthalic acids. The most preferred acids are terephthalic acid and mixtures of terephthalic and isophthalic acids.

The low molecular weight diols used in the preparation of the hard segments of the copolyesters have molecular weights of less than about 250. The term low molecular weight diol, as used herein, should be construed to include equivalent ester-forming derivatives. In this case, however, the molecular weight requirement pertains to the diol only and not to its derivatives.

Suitable low molecular weight diols which react to form the short chain ester units of the copolyesters include acyclic, alicyclic and aromatic dihydroxy compounds. The preferred diols are those with 2 to 15 carbon atoms such as ethylene, propylene, tetramethylene, isobutylene, pentamethylene, 2,2-dimethyltrimethylene, hexamethylene and decamethylene glycols, dihydroxy cyclohexane, cyclohexane dimethanol, resorcinol, hydroquinone, 1,5-dihydroxy naphthalene, and the like. Especially preferred are the aliphatic diols of 2 to 8 carbon atoms. Suitable bis-phenols include bis(p-hydroxy) diphenyl, bis(p-hydroxyphenyl) methane, bis(p-hydroxyphenyl) ethane, bis(p-hydroxyphenyl) propane and 2,2- bis(p-hydroxyphenyl) propane. Equivalent ester-forming derivatives of diols are also useful. For example, ethylene oxide or ethylene carbonate can be used in place of ethylene glycol.

The long chain glycols used to prepare the soft segments of these copolyesters have molecular weights of about 350 to 6000, and preferably about 600 to 3000. The chemical structure of the long chain polymeric part of the long chain glycol is not critical. Any substituent groups which do not interfere with the polymerization reaction to form the copolyester can be present. Thus, the chain can be a single divalent acyclic, alicyclic, or aromatic hydrocarbon group, poly(alkylene oxide) group, polyester group, a. combination thereof, or the like. Any of these groups can contain substituents which do not interfere to any substantial extent with the polymerization to form the copolyester used in accordance with this invention. The hydroxy functional groups of the long chain glycols used to prepare the copolyesters should be terminal groups to the extent possible.

Suitable long chain glycols which can be used in preparing the soft segments of the copolymers include poly- (alkylene ether) glycols in which the alkylene groups is of 2 to 9 carbon atoms such as poly(ethylene ether) glycols, poly(1,2- and 1,3-propylene ether) glycol, poly- (1,2-butylene ether) glycol, poly(tetramethylene ether) glycol, poly(pentamethylene ether) glycol, poly(hexamethylene ether) glycol, poly(heptamethylene ether) glycol, poly(octamethylene ether) glycol, poly(nonamethylene ether) glycol, and random or block copolymers thereof, for example, glycols derived from ethylene oxide and 1,2-propylene oxide.

Glycol esters of poly(alkylene oxide) dicarboxylic acids can also be used as the long chain glycol. These glycols may be added to the polymerization reaction or may be formed in situ by the reaction of a dicarboxymethyl acid of poly(alkylene oxide) such as HO OCCH (OCH CH CH CH OCH COOH with the low molecular weight diol, which is always present in a stoichiometric excess. The resulting poly(alkylene oxide) ester glycol then polymerizes to form G units having the structure -DOOCCH (OCH CH CH CH OCH2COOD- in which each diol cap (D) may be the same or different depending on whether more than one diol is used. These dicarboxylic acids may also react in situ with the long chain glycol, in which case a material is obtained having a formula the same as above except that the Ds are replaced with Gs, the polymeric residue of the long chain glycol. The extent to which this reaction occurs is quite small, however, since the low molecular weight diol is present in considerable excess.

Polyester glycols can also be used as the long chain glycol. In using polyester glycols, care must generally be exercised to control the tendency to interchange during melt polymerization. Certain sterically hindered polyesters, e.g.,

poly(2,2-dimethyl-1,3-propy1ene adipate), poly(2,2-dimethyl-1,3-propylene/2-methyl-2-ethyl-1,3-

propylene 2,5-dimethylterephthalate),

poly(2,2-dimethyl-1,3-propylene/2,2-diethyl-1,3-

propylene,

l,4-cyclohexanedicarboxylate), and

poly( 1,2-cyclohexylenedimethylene/2,2-dimethyl-l ,3-

propylene,

1,4-cyclohexanedicarboxylate) can be utilized under normal reaction conditions, and other more reactive polyester glycols can be used if proper reaction conditions, including a short residence time, are employed.

Suitable long chain glycols also include polyformals prepared by reacting formaldehyde with glycols such as pentamethylene glycol or mixtures of glycols such as a mixture of tetramethylene and pentamethylene glycols. Polythioether glycols also provide useful products. Polybutadiene and polyisoprene glycols, copolymers of these, and saturated hydrogenation products of these materials are also satisfactory long chain polymeric glycols. In addition, the glycol esters of dicarboxylic acids formed by oxidation of polyisobutylene-diene copolymers are useful raw materials. The preferred long chain glycols are poly (alkylene ether) glycols and glycol esters of poly(alkylene oxide) dicarboxylic acids.

The relative molecular weight of the segmented copolyester is expressed herein in terms of melt index, which is an empirical measurement of inverse melt viscosity. The segmented copolyester should have a melt index of less than about 150 in order to provide useful compositions. The melt indices specified herein are determined by the American Society for Testing and Materials (herein abbreviated ASTM) test method Dl238-65T using Condition L at 230 C. with a 2160 gram load.

It is required that the segmented copolyester have a melting point of at least about 125 C. in order to provide useful bonding agents. This is achieved by at least about percent by weight of the total low molecular weight diol and dicarboxylic acid being aromatic which provides the polyester with crystallizable short chain ester segments. Crystallinity in the short chain ester segments is increased by the use of more linear and symmetrical aromatic diacid. By linear aromatic diacid is meant a diacid in which each of the bonds between the carboxyl carbons and their adjacent carbons fall on a straight line drawn from one carboxyl carbon to the other. By symmetrical aromatic diacid is meant a diacid which is symmetrical with respect to a center line drawn from one carboxyl carbon to the other For example, repeating ester units such as tetramethylene terephthalate give an espe cially high melting short chain ester segment. On the other hand, when a non-linear and unsymmetrical aromatic diacid, such as isophthalic acid, is added to crystallizable short chain ester segments, their melting point is depressed. Preferably the segmented copolyester has a melting point of at least about 140 C.

The melting points specified herein are determined by differential thermal analysis. The melting point is read from the position of the endotherm peak in a thermogram when the sample is heated from room temperature at the rate of 10 C./min. The details of this method are described in many publications, for example, by C. B. Murphy in Difierential Thermal Analysis, R. C. Mackenzie, Editor, Volume I, Pages 643 to 671, Academic Press, New York, 1970.

The preferred segmented copolyester elastomers are those in which the dicarboxylic acid is aromatic dicarboxylic acid of 8 to 16 carbon atoms, the low molecular weight diol is aliphatic diol of 2 to -8 carbon atoms, the long chain glycol is poly(alkylene ether) glycol in which the alkylene group is of 2 to 9 carbon atoms, the short chain ester units amount to about 30 to 60 percent by weight of the copolyester, the long chain ester units amount to about 40 to 70' percent by weight of the copolyester, and the copolyester has a melt index of less than about 50 and a melting point of at least about C.

The copolyester elastomers prepared from terephthalic acid, or a mixture of terephthalic and isophthalic acids, 1,4-butanediol and polytetramethylene ether glycol having a molecular weight of about 600 to 3000 are particularly preferred for use in this invention. The raw materials are readily available, and the thread bonding properties of such polymers are outstanding.

The copolyester elastomers used as bonding agents in accordance with this invention can be made by conventional condensation polymerization procedures, as for example, in bulk or in a solvent medium which dissolves one or more of the monomers. They are conveniently prepared by a conventional ester interchange reaction. A preferred procedure involves heating the dimethyl ester of terephthalic acid, or a mixture of terephthalic and isophthalic acids, with a long chain glycol and an excess of a short chain diol in the presence of a catalyst at to 260 C., followed by distilling off the methanol formed by the interchange. Heating is continued until methanol evolution is complete. Depending on the temperature, catalyst and diol excess, this polymerization is complete within a few minutes to a few hours. This procedure results in the preparation of a low molecular weight prepolymer which can be converted to the high molecular weight segmented copolyester used in accordance with this invention.

These prepolymers can also be prepared by a number of alternate esterification or ester interchange processes. For example, the long chain glycol can be reacted with a high or low molecular weight short chain ester homopolymer or copolymer in the presence of catalyst until randomization occurs. The short chain ester homopolymer or copolymer can be prepared by ester interchange from either the dimethyl esters and low molecular weight diols, as above, or from the free acids with the diol acetates. Alternatively, the short chain ester copolymer can be prepared by direct esterification from appropriate diacids, anhydrides or acid chlorides, for example, with diols or by other processes such as reaction of the diacids with cyclic ethers or carbonates. Obviously the prepolymer can also be prepared by carrying out these processes in the presence of the long chain glycol.

The resulting prepolymer is then converted to the high molecular weight segmented copolyester elastomer by distillation of the excess of short chain diol. Best results are usually obtained if this final distillation is carried out at less than 1 mm. pressure and 240-260 C. for less than 2 hours in the presence of an antioxidant such as sym-di-beta-naphthyl-p-phenylenediamine or 1,3,5-trimethyl 2,4,6 tris[3,5-ditertiary-bntyl-4-hydroxybenzyl] benzene.

Most practical polymerization techniques rely upon ester interchange to complete the polymerization reaction. In order to avoid excessive hold times at high temperatures with possible irreversible thermal degradation, it is advantageous to employ a catalyst for the ester interchange reaction. While a wide variety of catalysts can be used, organic titanates such as tetrabutyl titanate, used alone or in combination with magnesium or zinc acetates, are preferred. Complex titanates, such as Mg[HlTi(OR derived from alkali or alkaline earth metal alkoxides and titanate esters are also very effective. Inorganic titanates such as lanthanum titanate, calcium acetate/antimony trioxide mixtures and lithium and magnesium alkoxides are representative of other catalysts which can be used.

While these condensation polymerizations are generally run in the melt without added solvent, it is sometimes advantageous to run them in the presence of inert solvent in order to facilitate removal of volatile products at lower than usual temperatures. This technique is especially valuable during prepolymer preparation, for

example, by direct esterification. However, certain low molecular weight diols, for example, butanediol in terphenyl, are conveniently removed during high polymerization by azeotropic distillation. Other special polymerization techniques, for example, interfacial polymerization of bisphenol with bisacylhalides and bisacylhalide capped linear diols, may prove useful for preparation of specific polymers.

The processes described above can be run both by batch and continuous methods. The preferred method for continuous polymerization, namely, ester interchange with a prepolymer, is a Well established commercial process.

The segmented copolyester may be used alone as the bonding agent for the thread or it may be modified to reduce its viscosity and to improve adhesion by mixing it with one or more low molecular weight thermoplastic resins which form compatible mixtures with the segmented copolyester, are thermally stable at about 150 C., and have melt viscosities of less than about 10,000 centipoises at 200 C. The term thermoplastic resin, as used throughout the specification and claims, is intended to include heat softenable resins, both natural and synthetic, as well as waxy types of materials. By the term compatible it is meant that there is no separation into distinct layers between the segmented copolyester and the low molecular weight resin or resins at the copolyester melt temperature. In some cases this compatibility is achieved in multi-component blends even though one of the low molecular weight thermoplastic resin components may not be compatible with the segmented copolyester elastomer alone. By the phrase thermally stable, it is meant that there is no significant permanent alteration in the properties of the resin after heating at the specified temperature for one hour in the presence of air. The melt viscosities specified herein are measured with a Brookfield viscometer by ASTM test method D1824-66 at elevated temperatures as indicated.

The low molecular weight thermoplastic resin may be added in an amount up to about 50 percent by weight, based on the segmented copolyester. Preferably the bonding agent contains less than about 10 percent by weight, based on the segmented copolyester, of low molecular weight thermoplastic resin.

Suitable low molecular weight thermoplastic resins for blending with the segmented copolyester elastomer include hydrocarbon resins, rosins, phenolic resins, chlorinated aliphatic hydrocarbon waxes, chlorinated polynuclear aromatic hydrocarbons, and the like.

The term hydrocarbon resins refers to hydrocarbon polymers derived from coke-oven gas, coal-tar fractions, cracked and deeply cracked petroleum stocks, essentially pure hydrocarbon feeds, and turpentines. Typical hydrocarbon resins include coumarone-indene resins, petroleum resins, styrene polymers, cyclopentadiene resins, and terpene resins. These resins are fully described in the Kirk- Othmer Encyclopedia of Chemical Technology, Second Edition, 1966, Interscience Publishers, New York, Volume 11, Pages 242 to 255.

The term coumarone-indene resins refers to hydrocarbon resins obtained by polymerization of the resin formers recovered from coke-oven gas and in the distillation of coal tar and derivatives thereof such as phenolmodified coumarone-indene resins. These resins are fully described in the Kirk-Othmer Encyclopedia, supra, Volume 11, pages 243 to 247.

The term petroleum resins refers -to hydrocarbon resins obtained by the catalytic polymerization of deeply cracked petroleum stocks. These petroleum stocks generally contain mixtures of resin formers such as styrene, methyl styrene, vinyl toluene, indene, methyl indene, butadiene, isoprene, piperylene and pentylenes. These resins are fully described in the Kirk-Othmer Encyclopedia, supra, Volume 11, Pages 248 to 250. The so-called polyalkylaromatic resins fall into this classification.

The term styrene polymers" refers to low molecular weight homopolymers of styrene as well as copolymers containing styrene and other comonomers such as alphamethyl-styrene, vinyl toluene, butadiene, and the like when prepared from substantially pure monomer.

The term cyclopentadiene resins refers to cyclopentadiene homopolymers and copolymers derived from coal tar fractions or from cracked petroleum streams. These resins are produced by holding a cyclopentadiene-containing stock at elevated temperatures for an extended period of time. The temperatures at which it is held determines whether the dimer, trimer, or higher polymer is obtained. These resins are fully described in the Kirk-Othmer Encyclopedia, supra, Volume 11, Pages 250 and 251.

The term terpene resins refers to polymers of terpenes which are hydrocarbons of the general formula C H occurring in most essential oils and oleoresins of plants, and phenol-modified terpene resins. Suitable terpenes include alpha-pinene, beta-pinene, dipentene, limonene, myrcene, bornylene, camphene, and the like. These products occur as by-products of coking operations of petroleum refining and of paper manufacture. These resins are fully described in the Kirk-Othmer Encyclopedia, supra, Volume 11, Pages 252 to 254.

The term rosins refers to the resinous materials that occur naturally in the oleoresin of pine trees, as well as derivatives thereof including rosin esters, modified rosins such as fractionated, hydrogenated, dehydrogenated and polymerized rosins, modified rosin esters, and the like. These materials are fully described in the Kirk- Othmer Encyclopedia, supra, Volume 17, Pages 475 to 505.

The term phenolic resins refers to the products resulting from the reaction of phenols with aldehydes. In addition to phenol itself, cresols, xylenols, p-tert.-buty1- phenol, p-phenylphenol and the like may be used as the phenol component. Formaldehyde is the most common aldehyde, but acetaldehyde, furfuraldehyde and the like may also be used. These resins are fully described in the Kirk-Othmer Encyclopedia, supra, Volume 15, Pages 176 to 207.

The term chlorinated aliphatic hydrocarbon waxes refers to those waxes which are commonly called chlorinated waxes such as chlorinated paraffin waxes. These waxes typically contain about 3070 percent by weight of chlorine. The term chlorinated polynuclear aromatic hydrocarbons refers to chlorinated aromatic hydrocarbons containing two or more aromatic rings such as chlorinated biphenyls, terphenyls, and the like, and mixtures thereof. These materials typically contain 30 to 70 percent by weight of chlorine.

The properties of the bonding agent can be further modified by the incorporation of thermally stable thermoplastic polymers of ethylenically unsaturated monomers including homopolymers of vinyl esters such as vinyl acetate, copolymers of these vinyl esters with other vinyl monomers such as ethylene, vinyl chloride and the like, and polymers of alkyl acrylates and methacrylates, or thermally stable condensation polymers such as polyesters and polyamides, and the like. For example, the addition of a copolymer of ethylene and vinyl acetate often increases the tackiness of the segmented copolyester elastomer. These modifying polymers typically have melt viscosities above about 10,000 centipoises at 200 C. and thus do not substantially reduce the viscosity of the segmented copolyester as do the low molecular weight thermoplastic resins defined above.

It is sometimes desirable to stabilize the segmented copolyester elastomer against the effects of heat or ultraviolet light. This can be done by adding stabilizers or antioxidants to the bonding agent. Satisfactory stabilizers comprise phenols and their derivatives, amines and their derivatives, compounds containing both hydroxyl and amine groups, hydroxyazines, oximes, polymeric phenolic esters, and salts of multivalent metals in which the metal is in its lower valence state.

Representative phenol derivatives useful as stabilizers include hydroquinone,

2,6-ditertiary-butyl-p-cresol,

tetrakis [methylene-3- 3 ,5 -ditertiary-butyl-4'-hydroxyphenyl) propionate] methane,

4,4'-bis(2,6-ditertiarybutylphenol),

1,3,5-trimethyl-2,4,6-tris [3,S-ditertiarybutyl-4-hydroxybenzyl] benzene, and

4,4'-butylidene-bis 6-tertiary-butyl-m-cresol) Various inorganic metal salts or hydroxides can be used as Well as organic complexes such as nickel dibutyl dithiocarbamate, manganous salicylate, and copper 3-phenylsalicylat'e. Typical amine stabilizers include aromatic amines such as N,N'-bis(beta-naphthyl)-p-phenylenediamine, N,N-bis(l-methylheptyl)-p-phenylene diamine, and either phenyl-beta-naphthyl amine or its reaction products with aldehydes. Mixtures of hindered phenols with esters of thiodipropionic acid, mercaptides and phosphite esters are particularly useful. Additional stabilization to ultraviolet light can be obtained by compounding with various UV absorbers such as substituted benzophenones or benzotriazoles.

The bonding agent can also be colored by the addition of organic or inorganic pigments or organic dyes where their effect is desired. Suitable inorganic pigments include rutile and anatase titanium dioxides, aluminum powder, cadmium sulfides and sulfo-selenides, lead antimonate, mercury cadmiums, chromates of nickel, tin and lead, ceramic greens such as chromium, cobalt, titanium and nickel oxides, ceramic blacks such as chromium, cobalt and iron oxides, carbon black, ultramarine blue, and the like. Suitable organic pigments include phthalocyanine blues and greens, quinacridones, and the like. Suitable dyes include disperse dyes such as Colour Index Disperse Blues 59, 63 and 64. Optical brightness such as Uvitex CF, sold by Ciba Corp., and Tinopal AN, sold by Geigy Chemical Corp., may also be incorporated where their effect is desired.

Plasticizers including phthalate esters such as dioctyl phthalate, and aryl phosphates such as tricresyl phosphate, and the like, may be added for applications where their effect is desired. Flame retardant additives, such as zinc borate, antimony trioxide, tris(2,3-dichloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, chlorinated waxes, and the like may be added, if desired. Other minor additives such as surfactants or lubricants may also be added, if desired.

The bonding agent may be applied to the multi-filament thread by dissolving the bonding agent in a suitable solvent and passing the thread through the solution. Suitable solvents for preparing these solutions include methylene chloride, ethylene dichloride, chloroform, trichloroethylene, and the like. The amount of bonding agent in the solution will vary depending upon the wetting characteristics of the particular thread and the amount of bonding agent desired on the thread. Generally the bonding agent pick-up by the thread should amount to about 1 to 10 percent by weight of the thread. Preferably the bonding agent pick-up is about 2 to 6 percent by weight. After the bonding agent has been applied, the coated thread is dried and may be stretched if desired.

The bonding agent may also be applied to the thread from an aqueous dispersion. Aqueous dispersions of the bonding agent can be prepared by dissolving the segmented copolyester and any other components of the bonding agent in a suitable water-immiscible organic solvent, emulsifying the organic solvent containing the segmented copolyester in water, and removing the organic solvent, as described by Funck and Wolff in US. Pat.

Sewing threads which have been bonded in accordance with this invention are useful in the manufacture of a wide variety of finished articles of commerce. These include articles from knit, felt, woven and non-woven cloth and fabrics, such as garments, bed clothes, table cloths, curtains, drapes, upholstery, umbrellas, flags, lamp shades, sleeping bags, parachutes, tents, nets, awnings, sails, hats, suspenders, gloves, neckties, carpets, rugs, conveyor belts, and the like; and articles from artificial leather and leather goods such as hand bags, gloves, shoes, belts, brief cases, suit cases, balls, clothes, and the like.

EXAMPLES OF THE INVENTION The following examples, illustrating the novel method of thread bonding of this invention, are given without any intention that the invention be limited thereto. All parts and percentages are by weight except as otherwise noted.

Example 1 (A) One pound of a segmented copolyester elastomer derived 31.6% from terephthalic acid, 9.2% from isophthalic acid, 16.6% from butanediol, and 42.6% from polytetramethylene ether glycol (PTMEG) having a molecular weight of about 1000, containing 52.6% short chain ester units, and having a melting point of 160 C. and a melt index of 15 was dissolved in one gallon of boiling methylene chloride and then allowed to cool to ambient temperature. Three ply Dacron polyester thread was coated with this solution. The coated thread was dried at 400 F. for five seconds. This operation resulted in 5% add-on Weight of the bonding resin. The coated thread was subsequently stretched at an elevated temperature and a silicone lubricant coating was applied to the coated thread.

The resulting coated thread had the following properties:

(1) The plies could not be separated by untwisting.

(2) The coating could not be peeled from the thread by abrasion.

(3) The coating possessed good heat dissipation as manifested by good slip characteristics through a sewing needle.

(4) There was no wicking of water into flexed thread over a twenty four hour period.

(5) The coated thread had good flexibility.

(B) The above procedure was repeated except that three ply nylon thread was used in place of the polyester thread. The resulting coated thread had the same excellent properties as those recited above.

(C) Procedure (A) above was again repeated except that a twisted bundle of continuous filament nylon thread was used in place of the polyester thread. The result was the same as above.

(D) Procedure (A) above was repeated except that a solvent mixture containing parts by volume of ethylene dichloride and 20 parts by volume of cyclohexane was used in place of methylene chloride. The result was the same as above.

(E) Procedure (A) above was repeated except that a solvent mixture containing 80 parts by volume of ethylene dichloride and 20 parts by volume of ethyl acetate was used in place of methylene chloride. The result was the same as above.

Example 2 To one gallon of boiling ethylene dichloride was added 0.95 pound of the segmented copolyester elastomer described in Example 1 and 0.05 pound of LTP 115, a phenol-modified terpene resin having a softening point of C. sold by Pennsylvania Industrial Chemical Corp. The solution was allowed to cool to room temperature. The LTP 115 softened (lowered initial modulus) the elastomer without having any significant effect on other properties as indicated in the following table.

Three ply Dacron thread was coated with the above solution as described in Example 1. The resulting coated thread had the same excellent properties as recited in Example 1 except that it exhibited even less tendency to increase in stiffness.

Example 3 Example 2 was repeated except that Piccolastic" A 50, a low molecular weight styrene homopolymer having a softening point of 50 C. and a melt viscosity of 29 centipoises at 190 C. sold b Pennsylvania Industrial Chemical Corp., was used in place of the LTP 115. The Piccolastic" A 50 softened the segmented copolyester elastomer while only slightly lowering the melting point and tensile strength. The resulting blend had a tensile strength of 4600 p.s.i., an elongation of 925%, an initial modulus of 7100 p.s.i. and a melting point of 155 C. Three ply Dacron thread was coated as in Example 2 with essentially the same result.

Example 4 A 9.5 g. portion of a segmented copolyester derived 44.4% from terephthalic acid, 18.8% from butanediol, and 36.8% from PTMEG having a molecular weight of 1000, containing 59.3% short chain ester units, and having a melting point of 203 C. and a melt index of 8 was dissolved in 200 ml. of boiling chloroform along with 0.5 g. of Piccolastic A 50 (Example 3). After cooling, 220 denier, 3 ply Dacron polyester thread was passed through the solution resulting in a 3 percent pick-up of the copolyester composition. The three plies were observed to be bonded together and did not unravel. The thread possessed good stiffness, but yet was still flexible. The coating also lowered the amount of fuzz on the surface of the thread.

Although the invention has been described and exemplified by way of specific embodiments, it is not intended that it be limited thereto. As will be apparent to those skilled in the art, numerous modifications and variations of these embodiments can be made without departing from the spirit of the invention or the scope of the following claims.

What is claimed is:

1. A bonded, flexible thread which comprises a multifilament thread selected from the group consisting of polyester thread and nylon thread coated with a bonding agent comprising a thermoplastic segmented copolyester elastomer consisting essentially of a multiplicity of recurring short chain ester units and long chain ester units joined through ester linkages, said short chain ester units amounting to to 65 percent by weight of said copolyester and being of the formula and said long chain ester units amounting to 35 to 85 percent by weight of said copolyester and being of the formula wherein R is the divalent aromatic radical remaining after removal of the carboxyl groups from dicarboxylic acid having a molecular weight of less than 350, D is the divalent radical remaining after removal of the hydroxyl groups from organic diol having a molecular weight of less than 250, and G is the divalent radical remaining after removal of the terminal hydroxyl groups from long chain glycol having an average molecular weight of 350 to 6000, said copolyester having a melt index of less than 150 and a melting point of at least C.

2. The bonded thread of Claim 1 in which the bonding agent also contains an aryl phosphate plasticizer.

3. The bonded thread of Claim 1 in which the dicarboxylic acid is aromatic dicarboxylic acid of 8 to 16 carbon atoms, the low molecular weight diol is aliphatic diol of 2 to 8 carbon atoms, and the long chain glycol is poly (alkylene ether) glycol in which the alkylene group is of 2 to 9 carbon atoms.

4. The bonded thread of Claim 3 in which the short chain ester units amount to about 30 to 60 percent by weight of the copolyester, the long chain ester units amount to about 40 to 70 percent by weight of the copolyester, and the copolyester has a melt index of less than 50 and a melting point of at least C.

5. The bonded thread of Claim 4 in which the aromatic dicarboxylic acid is selected from the group consisting of terephthalic acid, and mixtures of terephthalic and isophthalic acids, the low molecular weight diol is butanediol, and the long chain glycol is polytetramethylene ether glycol having a molecular weight of 600 to 3000.

6. The bonded thread of Claim 1 in which the bonding agent also contains up to 50 percent by Weight, based on said segmented copolyester elastomer, of low molecular weight thermoplastic resin which forms compatible mixtures with the segmented copolyester, is thermally stable at C., and has a melt viscosity of less than 10,000 centipoises at 200 C.

7. The bonded thread of Claim 6 in which the low molecular weight thermoplastic resin comprises one or more hydrocarbon resins, rosins, phenolic resins, chlorinated aliphatic hydrocarbon waxes, or chlorinated polynuclear aromatic hydrocarbons.

8. The bonded thread of Claim 6 in which the bonding agent comprises said segmented copolyester elastomer and less than 10 percent by weight, based on the segmented copolyester elastomer, of low molecular weight thermoplastic resin.

References Cited UNITED STATES PATENTS 2,698,817 1/1955 Guenther 117-138.8 3,187,752 6/1965 Glick 117-138.8 3,433,008 3/1969 Gage 28-75 3,013,914 12/1961 Willard 117-161 X 3,651,014 3/1972 Witsiepe 260-75 3,619,276 11/1971 Shimeha et al. 117-138.8 2,725,309 11/1955 Rodman 117-161 3,583,878 6/1971 Ragep et al. 117-161 3,034,920 5/1962 Waller 117-138.8 X 3,503,779 3/1970 Young et al. 117-161 3,502,620 3/1970 Caldwell 117-138.8 X 3,016,555 1/1962 Penoyer 117-161 X 2,752,320 6/1956 De Witt 117-161 3,296,172 1/1967 Funck et al 260-342 X FOREIGN PATENTS 779,054 7/ 1957 Great Britain.

WILLIAM D. MARTIN, Primary Examiner S. L. CHILDS, Assistant Examiner US. Cl. X.R.

28-75 R; 57-140 C; l17-138.8 N, 161 K, 161 UC may UNITED STATES PATENT FFlCE CERTFFICATE OF CORRECTION Pawnt No. 3 Dated -#9, 197

appemza 121 the above-identified patent It is certified that error eby corrected as @hown below:

and that said-Letters Patent are her Column 1, line 6, after "M092" should be inserted assignorato E. I. du Pont de Nemours and Company, Wilmington, Del.

Signed and sealed this 29th day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

